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Old 28-03-2008, 09:07   #1
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Bent Steel Davit Claims

Hey everyone, I was just looking through the April 2008 Cruising World and came across a claim that I think should be noted by some of the members on these boards. I won't get into any names or specifics but this could help someone avoid an unfortunate incident.

There is a set of bent, 304 stainless steel davits advertised that makes the claim of being able to safely handle 350 lbs. As a comparison, a quality davit manufacturer would only make stainless steel tubular davits that are rated up to 275 lbs. and that is with several features that are not included with this welded/bent system

A welded, bent steel davit will never be able to handle the forces that a 350 lb. tender will exert while operating. As I have mentioned in previous posts, when a steel tube is bent, the thickness is spread out at the bend, greatly reducing any strength. Simply put, a bent piece of steel will want to keep bending while under load.

The problem with welding components such as the compression strut, other than eventual unsightly corrosion at the weld, is that it only gives the illusion of strength. Instead of transferring the load downwards, as an independent strut would accomplish, a welded strut is acting only to hold the system together.

Another problem is that these types of systems are not adjustable to fit the needs of a sailor. Once the weld is made, that’s it, no more adjustments. A truly customizable system would have the ability to change heights and angles while maintaining superior strength.

These two photos show a welded, bent steel 350 lb. model davit and a 350lb. davit cast out of Almag-35. The cast model is also equipped with a 7:1 purchase while the bent davits only provide an insufficient 4:1. Take a look at each photo and let me know what you think. Those of you who are considering davits should take these points to heart, and those that already have a set of bent steel davits should consider making the switch.

Just a note, the extra hardware on the cast system on the right was added by the customer so that he could mount various items like a flag pole, etc.
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Old 28-03-2008, 14:18   #2
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Are those aluminum castings and stainless tubes and bolts? If so I would love to see these units after they have been in salt water for a few years. Is that why I only saw boats from Toronto?
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Old 28-03-2008, 14:24   #3
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Where's my 'grain of salt"????
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Old 28-03-2008, 14:30   #4
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Unsolicited posting from a vendor? This belongs in the Vendor's forum.
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Old 28-03-2008, 15:04   #5
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Originally Posted by DeepFrz View Post
Are those aluminum castings and stainless tubes and bolts? If so I would love to see these units after they have been in salt water for a few years. Is that why I only saw boats from Toronto?
Every touch point between any steel tube against aluminum has a delron sleeve to prevent the issues surrounding dissimilar metals which you alluded to. Any nut/bolt has a stainless helicoil with Teff-gel to prevent any corrosion there. The pictures are from Toronto because that is where I live and have my camera. However, there are many examples that show these products in salt water.
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Old 28-03-2008, 15:16   #6
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Unsolicited posting from a vendor? This belongs in the Vendor's forum.
This has been discussed with the moderators. This post/thread is about how to avoid getting into a bad situation with bent steel davits. As far as I am concerned, there is no place for bent steel davits. This is what the post is in regards to.

As far as being an "unsolicited post"; I consider myself to be somewhat experienced in the area of davits. Yes, this is partly because I make them, and I am very proud of what we do. Therefore, when I see a bad situation I feel like it is a responsibility to make it known to others, solicited or not. I apologize if I have offended you by placing this post on a forum that you disprove of, but hope that you will continue to allow the moderators to police the boards.

Thank you, and if there are any other questions surrounding any of the points that I brought up in the post, I would like to have a chance to answer them.
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Old 29-03-2008, 09:00   #7
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Are you suggesting it's a problem with being bent, or being welded?
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Old 29-03-2008, 09:27   #8
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Are you suggesting it's a problem with being bent, or being welded?
Both, because most bent steel davits are held together with welds. Bending is a very inefficient way to join tubes and make angles with them. Instead of keeping the integrity of the metal, a bend spreads out the wall thickness of the tube at each and every bend. It's important to note that these are also the areas under the highest load.

Welds are used in these bent systems because they have not been designed with an innovative way to join different sections. The least creative solution is to make a weld. Welds are also points where corrosion will attack because the welding material and methods are often below true marine-grade standards. Welds are also inherently weaker than a casting joint.
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Old 29-03-2008, 14:53   #9
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In your opinion Ben. Personaly I really don't agree with your comments. I happen to have custom made SST Davits that have wleds and bends and it is strong, never had a problem and I stand by it's strength. Sure you could argue a point that a cast is stronger. But if the Davit is a good design, has been made well from the begining, then it will have no problems. I suspend a 3.5m inflatable with solid ply floor, inflatable Keel, with a 15Hp outboard and full fuel tank and anchor from my Davits. And I have also stood inside the inflatable while suspended. No problems. The greatest weight it had to enjure was when the drain hole got blocked ant the inflatable filled with water. I don't know what the thing must have weighed, but we would talking tons. In the end, the attachment points on inflatable gave way, not the Davits. Of and I also have the Mizzen sheet travelr mounted to the top of the Davits. So they take a lot or sideways and lifting force as well.
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Old 29-03-2008, 16:07   #10
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Sure you could argue a point that a cast is stronger.
This is basically my point. I agree that a system could be welded and bent together but that it would require thicker walled and higher OD stainless steel, increasing the weight dramatically. The original post was about a bent system that is rated at 350 lbs. and the weight of your tender + gear, etc. is no more that 250-275 lbs. (in my opinion, I could be wrong and would definitely confirm before suggesting any equipment choices.)

Usually bent steel davits don't have many problems while youíre tied up at the dock. Itís when youíre at sea and the tender is being slammed up and down. Even in moderate, Sunday afternoon conditions, the extra load experienced on the davits by the tender while underway is considerable. I have seen many, many bent steel configurations buckle under these loads.

I don't think that there is any question about how a stainless steel tube weakens as it is bent. When the steel is originally produced, the 'grain' sets up in a certain direction, contributing to much of the final strength. By bending the tube, you break that configuration and make the metal pliable again.

Have you experienced any corrosion at the welds? In my experience this often the first place that you will see salt water reacting with your hardware.

These are my opinions and I stand behind them. However, I appreciate any debate and dialogue as I see it as a chance to add to my experience.
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Old 29-03-2008, 16:22   #11
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... As far as I am concerned, there is no place for bent steel davits. ....";......

because I make them, ....
Nicolle and I have been a bit surprised about some of the cultural differences in the US from home in Aus. We are stuck, waiting for our boat to be ready and the TV has been on a bit. Cable from the US.

Its surprising how many TV advertisers slag off the opposition including quoting of names.

I am sure that I don't like it! Call me weird, but I don't mind people telling me how their product is good and what their Unique Competitive Advantage is, but I don't like belittling of the opposition. Iím not a mod here so policy is nothing to do with me, and Iím not trying to tell the mods my thoughts. Iím just telling Ben my thoughts. There is a spot on this forum you can tell us all about your product (even give us a special offer to save us some cash!) but please I'm only interested in what you tell us about your product, not what you feel about someone elseís.

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Old 29-03-2008, 16:31   #12
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These opinions come from experience that I have accumulated by building my own bent system. A decade ago, we experimented with a bent steel model, called the Euro-Lift and ultimately had it scrapped for many of the reasons that I have described. I would not offer an opinion that I developed by conjecture, bias or heresy and generally will try anything to solve a problem. My conclusions come from a trial and error approach and this has served to create some great solutions.
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Old 29-03-2008, 16:47   #13
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These opinions ....
Thats the point, yours are only opinions.

Our Advertising Standards say your opinions must be more carefully couched in advertising:

Quote:

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which is likely to cause damage to the business or goodwill

of a competitor.
http://www.adstandards.com.au/pages/...hics_final.pdf

The point is no court or legislation has made your competitors products illegal. They can claim you misrepresent the facts. As the advertising medium (CF etc) cant investigate all statements then they can not determain misrepresentation.

So what you are saying may well be ok for some cultures used to slagging off the competitors. But the tactic wont work with all. We are not used to it.

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Old 29-03-2008, 17:03   #14
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I am just going through this same dilemma with a welder who strongly advises against bends on stainless pipe for a heavy load bearing weight that is subject to momentum in a seaway.

Obviously any system is only as strong as its weakest point, which you have correctly pointed out are the bends.

Ben, the silent majority thanks you for your caution!
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Old 29-03-2008, 17:38   #15
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Thank you, Pelagic. Safety first is what I say.

MarkJ, this is not an advertisement, it is merely a commentary on a technique that is used throughout the industry. I 'slag' no one and only want to highlight some of the issues surrounding the subject. As far as my opinions go, I have no reservations about expressing them and the only rules surrounding this is that they must be separated from my professional opinions.

I come from a culture that uses the scientific exchange of ideas to come up with better solutions. This means the careful examination of every method and material and then making choices based how they perform. I submit to you that this is an exercise in solving problems, not engaging in slander.
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